Endoscopic surgical procedures are routinely performed in order to accomplish various surgical tasks. In an endoscopic surgical procedure, small incisions, called portals, are made into the patient. An endoscope, which is a device that allows medical personnel to view the surgical site, in inserted in one of the portals. Surgical instruments used to perform a specific surgical task are inserted into other of the portals. The surgeon views the surgical site through the endoscope to determine how to manipulate the surgical instruments in order to accomplish the surgical procedure. An advantage of performing endoscopic surgery is that since the portions of the body that are cut open are minimized, the portions of the body that need to heal after surgery are likewise reduced. Moreover, during an endoscopic surgical procedure, only a relatively small portions of the patient's internal organs and tissue are exposed to the open environment. This minimal opening of the patient's body lessens the extent to which a patient's organs and tissue are open to infection.
The ability to perform endoscopic surgery has been enhanced by the development of powered surgical tools especially designed to perform endoscopic surgical procedures. One such tool, for example, is sold by the Applicant's Assignee under the trademark HUMMER II. This tool is in form of a cylindrical handpiece designed to be held in the hand of the surgeon. Internal to the handpiece there is a motor. A front end of the handpiece is provided with a coupling assembly for releasably holding a cutting accessory. The types of cutting accessories that are attached to these handpiece include edgers, resectors, planers and burrs. Integral with the motor and coupling assembly is a means for transmitting the rotary power developed by the motor to the cutting accessory.
The handpiece also has a suction conduit. This is because, in an endoscopic surgical procedure, irrigating fluid is introduced into the surgical site. This fluid serves as a transport media for removing tissue and debris from the surgical site. In order to remove the irrigating fluid, and the material in the fluid, a suction path is provided through the cutting accessory and the handpiece. A suction pump is connected to the handpiece and provides the suction force for drawing the fluid and material away from the surgical site. In order to control the suction flow through the cutting accessory and the handpiece, the handpiece is provided with a manually operated valve. Thus, with a single handpiece, a surgeon both manipulates the cutting accessory and control the suction of material away from the surgical site.
While current powered surgical handpiece have proven to be useful tools, they are expensive to manufacture and can be difficult to maintain. This is because the handpiece, which is typically less than 14 cm long and less than 3 cm in diameter, must contain the motor, the coupling assembly, the suction conduit and the valve for controlling fluid flow through the suction conduit. Each of these subassemblies has a number of components that must cooperate with the complementary components of the handpiece. For example, the motor is often provided with a speed reducing/torque increasing planetary gear assembly. This assembly includes a fixed ring gear. Given the relatively small size of this ring gear, and the forces to which it is subjected, the gear is typically manufactured from stainless steel. Thus, this gear is provided as a stand-alone component internal to the handpiece.
Also, many handpieces are provided with lever-set suction valves for regulating fluid flow through the suction conduit. This type of valve includes a valve body that is rotatably fitted in the handpiece. Bosses extend outwardly from the opposed ends of the valve body through the handpiece. The bosses are connected to exposed levers on the handpiece that a surgeon pivots to set the valve. An advantage of this arrangement is that once assembled, the valve is essentially a single moving part. However, this assembly is formed out of numerous components.
Moreover, the coupling assemblies of many powered endoscopic surgical handpieces are likewise formed out of numerous components. This is because these assemblies typically must be designed to hold the rotating member of the cutting accessory to a complementary element integral with the gear train, hold a static outer shell of the cutting accessory in place, and provide a seal around the rotating member in order to ensure that there will be good suction flow through the rotating member. Currently, some of these coupling assemblies are constructed so that, once assembled, they are difficult, if not impossible, to disassemble. The difficulty associated with disassembling these coupling assemblies makes it difficult to perform maintenance on the handpieces with which they are associated.
Thus, collectively, having to provide the numerous components of the current endoscopic handpieces and that fact that some of their components cannot be readily disassembled makes it relatively expensive to both provide and maintain these handpieces.